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Pulp, skin and seeds: what each part of the grape gives wine

Sugar and acid from the pulp, colour, tannin and aroma from the skin, harsher tannin from the seeds. How each part of the grape shapes red, white, rosé and orange wine.

Updated October 2026

Rewritten by Alper Billik, Advanced Sommelier

4 min read

The short answer: the pulp gives the juice: water, sugar and acid. The skin gives colour, most of red wine's tannin and much of the aroma. The seeds give tannin too, but harsher, so winemakers handle them with care. Every wine style is a choice about how much of each part to use.

The pulp: water, sugar and acid

  • Most of the berry is pulp, and most of the pulp is water.
  • Sugars: mainly glucose and fructose. Yeast turns them into alcohol, so riper grapes mean more potential alcohol.
  • Acids: mainly tartaric and malic. Malic acid falls as the grape ripens, which is one reason wines from cool places taste sharper.
  • Colourless: the juice of almost every grape is clear, black grapes included. That is why a white wine can be made from black grapes (Blanc de Noirs). The exceptions are teinturier grapes, such as Alicante Bouschet and Saperavi, which have red flesh.

The skin: colour, tannin and aroma

  • Colour: red and purple pigments called anthocyanins sit in the skins of black grapes. Red wine is red only because the juice spends time with the skins.
  • Tannin: skin tannins give red wine its grip and structure. The longer the skins stay in the wine (maceration), the more is extracted.
  • Aroma: much of a grape's aroma, and the precursors that become aroma, sit in and just under the skin. Some white winemakers give the crushed grapes a few hours of skin contact before pressing to capture more.
  • Thickness matters: thick-skinned Cabernet Sauvignon gives deep colour and firm tannin; thin-skinned Pinot Noir gives paler, softer wine. (More on why Pinot Noir is a diva.)
  • The bloom: the dusty, waxy layer on the skin, home to wild yeasts that can start a spontaneous fermentation.

The seeds: handle with care

  • Seed tannins are harsher and more bitter than skin tannins, especially when the seeds are unripe.
  • Winemakers avoid crushing seeds: gentle presses, careful pumping, no grinding.
  • More comes out as alcohol rises during fermentation and with a long maceration, so winemakers taste daily and decide when to press.
  • Growers taste seeds too. Brown, crunchy, nutty seeds are a sign of ripe tannins; green, bitter ones say wait.

And the stems

Most grapes are destemmed, but some winemakers ferment whole bunches, stems and all, especially with Pinot Noir and Syrah. Stems add tannin and a fresh, sometimes herbal lift. Whole uncrushed berries are also the start of carbonic maceration.

How each style uses the grape

White
What happensGrapes pressed, juice fermented without skins
What it takes from the grapeMostly pulp
Rosé
What happensBlack grapes, a few hours of skin contact or a direct press
What it takes from the grapePulp and a little skin colour
Red
What happensJuice fermented with skins and seeds for days or weeks
What it takes from the grapePulp, skins and seeds
Orange (skin-contact white)
What happensWhite grapes fermented on their skins
What it takes from the grapePulp, plus skin colour, tannin and texture
Blanc de Noirs
What happensBlack grapes pressed gently and quickly
What it takes from the grapeClear juice from the pulp

Before any of this, a flower has to become a berry, and not all of them do: see coulure and millerandage. After fermentation, malolactic fermentation softens the pulp's malic acid. For a lighter take on grape personalities, try why white and red grapes need therapy.

Quick quiz

Question 1

Where does the colour of red wine come from?

  1. a)The pulp
  2. b)The skins
  3. c)The seeds
  4. d)The oak barrel
Show answer

b) The skins. Anthocyanins in the skins of black grapes. The juice itself is clear.

Question 2

What are the two main acids in grapes?

  1. a)Citric and lactic
  2. b)Acetic and malic
  3. c)Tartaric and malic
  4. d)Tartaric and lactic
Show answer

c) Tartaric and malic. Tartaric and malic. Lactic acid appears in wine after malolactic fermentation.

Question 3

What is a teinturier grape?

  1. a)A grape with red flesh
  2. b)A grape with no seeds
  3. c)A grape used only for rosé
  4. d)A grape grown on its own roots
Show answer

a) A grape with red flesh. Teinturier grapes, such as Alicante Bouschet, have red flesh as well as dark skins.

Question 4

Why do winemakers avoid crushing the seeds?

  1. a)They add sugar
  2. b)They give harsh, bitter tannins
  3. c)They turn the wine white
  4. d)They stop fermentation
Show answer

b) They give harsh, bitter tannins. Seed tannins are harsher than skin tannins, above all when the seeds are unripe.

Question 5

How can a white wine be made from black grapes?

  1. a)By adding sulfur
  2. b)By pressing gently so the juice takes almost no colour
  3. c)By ageing in old oak
  4. d)By blending with white wine
Show answer

b) By pressing gently so the juice takes almost no colour. The colour is in the skins, so clear juice pressed quickly stays white: Blanc de Noirs.

Study with SOMM DIGI AILevel 1 practice test

Questions people ask

Which part of the grape gives tannin?

Mainly the skins and the seeds, and the stems if whole bunches are used. Seed and stem tannins are the harsher ones.

Why is the juice of black grapes clear?

The colour pigments, anthocyanins, are in the skin, not the pulp. Only teinturier grapes have red flesh.

Do white wines have tannin?

Very little, because the juice is separated from the skins early. Skin-contact (orange) wines have noticeably more.

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